Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 03061462 2019-10-24
1
CONTROL SYSTEM FOR WORK VEHICLE, METHOD, AND WORK VEHICLE
TECHNICAL FIELD
[0001] The present invention relates to a control system for a work
vehicle, a method,
and a work vehicle.
BACKGROUND ART
[0002] The ground surface on which work is performed by a work vehicle does
not
always have a flat shape but usually has an undulation. Patent Document 1
discloses a
technique for determining a size of undulation on the ground surface and
determining a
digging start position according to the size of the undulation. Specifically,
when the
undulation is small, the controller determines a digging start position to be
at a base of the
undulation. When the undulation is large, the controller determines a digging
start
position to be at a position between a base and a peak of the undulation.
CITATION LIST
PATENT DOCUMENT
[0003] Patent Document 1: US Patent Publication No. 7,509,198
SUMMARY OF THE INVENTION
Technical Problem
[0004] However, a magnitude of the load on a work implement varies
depending on
whether a gradient is an upward gradient or a downward gradient. Because the
above
technique cannot handle different types of gradients, the load on the work
implement may
become excessive, or work efficiency may be reduced.
[0005] An object of the present invention is to provide a control system
for a work
vehicle, a method, and a work vehicle that enable to prevent a load on a work
implement
from becoming excessive while improving work efficiency.
CA 03061462 2019-10-24
2
SOLUTION TO PROBLEM
[0006] A control system according to a first aspect is a control system for
a work
vehicle including a work implement. The control system includes a controller.
The
controller is programmed to execute the following processing. The controller
acquires
actual topography data indicating an actual topography to be worked. The
controller
determines a target design topography indicating a target trajectory of the
work implement
based on the actual topography. The controller determines whether the actual
topography
is an upward gradient or a downward gradient based on the actual topography
data. The
controller changes the target design topography according to a result of
determination of
the gradient.
[0007] A method according to a second aspect is a method executed by a
controller for
setting a target trajectory of a work implement of a work vehicle. The method
includes
the following processing. A first process is to acquire actual topography data
indicating
an actual topography to be worked. A second process is to determine a target
design
topography indicating a target trajectory of a work implement based on the
actual
topography. A third process is to determine whether the actual topography is
an upward
gradient or a downward gradient based on the actual topography data. A fourth
process is
to change the target design topography according to a result of determination
of the
gradient.
[0008] A work vehicle according to a third aspect is a work vehicle
including a work
implement and a controller that controls the work implement. The controller is
programmed to execute the following processing. The controller acquires actual
topography data indicating an actual topography to be worked. The controller
determines
a target design topography indicating a target trajectory of the work
implement based on
the actual topography. The controller determines whether the actual topography
is an
upward gradient or a downward gradient based on the actual topography data.
The
controller changes the target design topography according to a result of
determination of
1 . 1
CA 03061462 2019-10-24
)
3
the gradient. The controller outputs a command signal for controlling the work
implement according to the target design topography.
ADVANTAGEOUS EFFECTS OF INVENTION
[0009] In the present invention, a target design topography is
determined based on an
actual topography, and the target design topography is changed according to a
result of
determination as to whether the actual topography is an upward gradient or a
downward
gradient. As a result, a load on the work implement can be prevented from
becoming
excessive while work efficiency can be improved.
BRIEF DESCRIPTION OF DRAWINGS
[0010] FIG. 1 is a side view of a work vehicle according to an
embodiment.
FIG. 2 is a block diagram of a drive system and a control system of the work
vehicle.
FIG. 3 is a schematic view of a configuration of the work vehicle.
FIG. 4 is a flowchart illustrating automatic control processing of a work
implement.
FIG. 5 is a graph illustrating an example of an actual topography before and
after
smoothing processing.
FIG. 6 is a graph illustrating an example of an actual topography, a final
design topography
and a target design topography.
FIG. 7 is a graph illustrating an example of target parameter data.
FIG. 8 is a flowchart illustrating processing for determining a target
displacement.
FIG. 9 is a flowchart illustrating processing for determining a correction
coefficient.
FIG. 10 is a graph illustrating an example of an inclination degree parameter.
FIG. 11 is a graph illustrating a definition of an inclination degree
parameter.
FIG. 12 is a block diagram of a configuration of a control system according to
a first
modified example.
FIG. 13 is a block diagram of a configuration of a control system according to
a second
modified example.
CA 03061462 2019-10-24
4
FIG. 14 is a graph illustrating another example of target parameter data.
FIG. 15 is a graph illustrating another example of an inclination degree
parameter.
DESCRIPTION OF EMBODIEMENT
[0011] A work vehicle according to an embodiment will now be described with
reference to the drawings. FIG. 1 is a side view of a work vehicle 1 according
to an
embodiment. The work vehicle 1 according to the present embodiment is a
bulldozer.
The work vehicle 1 includes a vehicle body 11, a travel device 12, and a work
implement
13.
[0012] The vehicle body 11 includes an operating cabin 14 and an engine
compartment
15. An operator's seat that is not illustrated is disposed in the operating
cabin 14. The
engine compartment 15 is disposed in front of the operating cabin 14. The
travel device
12 is attached to a bottom portion of the vehicle body 11. The travel device
12 includes a
pair of right and left crawler belts 16. Only the left crawler belt 16 is
illustrated in FIG. 1.
The work vehicle 1 travels due to the rotation of the crawler belts 16. The
travel of the
work vehicle 1 may be either autonomous travel, semi-autonomous travel, or
travel under
operation by an operator.
[0013] The work implement 13 is attached to the vehicle body 11. The work
implement 13 includes a lift frame 17, a blade 18, and a lift cylinder 19.
[0014] The lift frame 17 is attached to the vehicle body 11 so as to be
movable up and
down around an axis X extending in the vehicle width direction. The lift frame
17
supports the blade 18. The blade 18 is disposed in front of the vehicle body
11. The
blade 18 moves up and down as the lift frame 17 moves up and down.
[0015] The lift cylinder 19 is coupled to the vehicle body 11 and the lift
frame 17.
Due to the extension and contraction of the lift cylinder 19, the lift frame
17 rotates up and
down around the axis X.
[0016] FIG. 2 is a block diagram of a configuration of a drive system 2 and
a control
system 3 of the work vehicle 1. As illustrated in FIG. 2, the drive system 2
includes an
t . , CA 03061462 2019-10-24
engine 22, a hydraulic pump 23, and a power transmission device 24.
[0017]
The hydraulic pump 23 is driven by the engine 22 to discharge hydraulic
fluid.
The hydraulic fluid discharged from the hydraulic pump 23 is supplied to the
lift cylinder
19.
Although only one hydraulic pump 23 is illustrated in FIG. 2, a plurality of
hydraulic
pumps may be provided.
[0018]
The power transmission device 24 transmits driving force of the engine 22 to
the travel device 12. The power transmission device 24 may be a hydro static
transmission (HST), for example. Alternatively, the power transmission device
24 may
be, for example, a torque converter or a transmission having a plurality of
transmission
gears.
[0019]
The control system 3 includes a first operating device 25a and a second
operating device 25b. The first operating device 25a and the second operating
device 25b
are disposed in the operating cabin 14. The first operating device 25a is a
device for
operating the travel device 12. The first operating device 25a receives an
operation by the
operator for driving the travel device 12, and outputs an operation signal in
response to the
operation.
[0020]
The second operating device 25b is a device for operating the work implement
13.
The second operating device 25b receives an operation by the operator for
driving the
work implement 13, and outputs an operation signal in response to the
operation. The
first operating device 25a and the second operating device 25b include, for
example, an
operating lever, a pedal, a switch, or the like.
[0021]
The first operating device 25a is configured to be operable at a forward
position, a reverse position, and a neutral position. An operation signal
indicating a
position of the first operating device 25a is output to the controller 26.
When the
operating position of the first operating device 25a is in the forward
position, the controller
26 controls the travel device 12 or the power transmission device 24 so that
the work
vehicle 1 moves forward. When the operating position of the first operating
device 25a is
in the reverse position, the controller 26 controls the travel device 12 or
the power
i 1 .
. CA 03061462 2019-10-24
6
transmission device 24 so that the work vehicle 1 moves in reverse.
[0022] The second operating device 25b is configured to be
operable at a raising
position, a lowering position, and a neutral position. An operation signal
indicating a
position of the second operating device 25b is output to the controller 26.
When the
operating position of the second operating device 25b is in the raising
position, the
controller 26 controls the lift cylinder 19 so that the blade 18 is raised.
When the
operating position of the second operating device 25b is in the lowering
position, the
controller 26 controls the lift cylinder 19 so that the blade 18 is lowered.
[0023] The control system 3 includes an input device 25c and a
display 25d. The
input device 25c and the display 25d are, for example, touch screen-type
display input
devices. The display 25d is, for example, an LCD or an OLED. The display 25d
may be
another type of display device. The input device 25c and the display 25d may
be separate
devices. For example, the input device 25c may be another input device such as
a switch.
The input device 25c may be a pointing device such as a mouse or a trackball.
The input
device 25c outputs an operation signal indicating an operation by the operator
to the
controller 26.
[0024] The control system 3 includes a controller 26, a storage
device 28, and a
control valve 27. The controller 26 is programmed to control the work vehicle
1 based on
acquired data. The controller 26 includes, for example, a processor such as a
CPU. The
controller 26 acquires an operation signal from the operating devices 25a and
25b. The
controller 26 controls the control valve 27 based on the operation signal. The
controller
26 acquires an operation signal from the input device 25c. The controller 26
outputs a
signal to display a predetermined screen on the display 25d. The controller 26
is not
limited to one unit and may be divided into a plurality of controllers.
[0025] The control valve 27 is a proportional control valve and
is controlled by a
command signal from the controller 26. The control valve 27 is disposed
between a
hydraulic actuator such as the lift cylinder 19 and the hydraulic pump 23. The
control
valve 27 controls the flow rate of the hydraulic fluid supplied from the
hydraulic pump 23
$ , CA 03061462 2019-10-24
7
to the lift cylinder 19. The controller 26 generates a command signal to the
control valve
27 so that the blade 18 operates in response to an operation of the second
operating device
25b. As a result, the lift cylinder 19 is controlled in response to an
operation amount of
the second operating device 25b. The control valve 27 may be a pressure
proportional
control valve. Alternatively, the control valve 27 may be an electromagnetic
proportional
control valve.
[0026] The control system 3 includes a work implement sensor 29.
The work
implement sensor 29 senses a position of the work implement and outputs a work
implement position signal indicating the position of the work implement.
Specifically,
the work implement sensor 29 senses the stroke length of the lift cylinder 19
(hereinafter
referred to as "lift cylinder length L"). As illustrated in FIG. 3, the
controller 26
calculates a lift angle Olift of the blade 18 based on the lift cylinder
length L. FIG. 3 is a
schematic view of a configuration of the work vehicle 1.
[0027] In FIG. 3, the origin position of the work implement 13
is illustrated as a chain
double-dashed line. The origin position of the work implement 13 is the
position of the
blade 18 in a state where the tip of the blade 18 is in contact with the
ground surface on a
horizontal ground surface. The lift angle Olift is the angle from the origin
position of the
work implement 13.
[0028] As illustrated in FIG. 2, the control system 3 includes a
position sensor 31.
The position sensor 31 measures a position of the work vehicle 1. The position
sensor 31
includes a global navigation satellite system (GNSS) receiver 32 and an IMU
33. The
GNSS receiver 32 is, for example, a receiver for global positioning system
(GPS). An
antenna of the GNSS receiver 32 is disposed on the operating cabin 14. The
GNSS
receiver 32 receives a positioning signal from a satellite and calculates the
position of the
antenna based on the positioning signal to generate vehicle body position
data. The
controller 26 acquires the vehicle body position data from the GNSS receiver
32. The
controller 26 acquires the traveling direction and vehicle speed of the work
vehicle 1 from
the vehicle body position data.
r r ,
CA 03061462 2019-10-24
8
[0029] The IMU 33 is an inertial measurement unit. The IMU 33 acquires
vehicle
body inclination angle data. The vehicle body inclination angle data includes
an angle
(pitch angle) with respect to the horizontal in the vehicle longitudinal
direction and an
angle (roll angle) with respect to the horizontal in the vehicle lateral
direction. The
controller 26 acquires the vehicle body inclination angle data from the IMU
33.
[0030] The controller 26 calculates a blade tip position PO from the
lift cylinder length
L, the vehicle body position data, and the vehicle body inclination angle
data. As
illustrated in FIG. 3, the controller 26 calculates global coordinates of the
GNSS receiver
32 based on the vehicle body position data. The controller 26 calculates the
lift angle
Olift based on the lift cylinder length L. The controller 26 calculates the
local coordinates
of the blade tip position PO with respect to the GNSS receiver 32 based on the
lift angle
Olift and the vehicle body dimension data. The vehicle body dimension data is
stored in
the storage device 28 and indicates the position of the work implement 13 with
respect to
the GNSS receiver 32. The controller 26 calculates the global coordinates of
the blade tip
position PO based on the global coordinates of the GNSS receiver 32, the local
coordinates
of the blade tip position PO, and the vehicle body inclination angle data. The
controller
26 acquires the global coordinates of the blade tip position PO as blade tip
position data.
[0031] The storage device 28 includes, for example, a memory and an
auxiliary
storage device. The storage device 28 may be, for example, a RAM or a ROM. The
storage device 28 may be a semiconductor memory, a hard disk, or the like. The
storage
device 28 is an example of a non-transitory computer-readable recording
medium. The
storage device 28 stores computer commands that are executable by the
processor and for
controlling the work vehicle 1.
[0032] The storage device 28 stores design topography data and work
site topography
data. The design topography data indicates a final design topography. The
final design
topography is the final target shape of the surface of the work site. The
design
topography data is, for example, a construction drawing in a three-dimensional
data format.
The work site topography data indicates an actual topography of the work site.
The work
= t = =
CA 03061462 2019-10-24
9
site topography data is, for example, an actual topography survey map in a
three-dimensional data format. The work site topography data can be acquired
by aerial
laser survey, for example.
[0033] The controller 26 acquires actual topography data. The
actual topography
data indicates an actual topography of the work site. The actual topography of
the work
site is an actual topography of a region along the traveling direction of the
work vehicle 1.
The actual topography data is acquired by calculation in the controller 26
from the work
site topography data, and the position and traveling direction of the work
vehicle 1
acquired from the aforementioned position sensor 31.
[0034] The controller 26 automatically controls the work
implement 13 based on the
actual topography data, the design topography data, and the blade tip position
data. The
automatic control of the work implement 13 may be semi-automatic control
performed in
combination with manual operation by the operator. Alternatively, the
automatic control
of the work implement 13 may be a fully automatic control performed without
manual
operation by the operator.
[0035] The automatic control of the work implement 13 in digging
executed by the
controller 26 will be described below. FIG. 4 is a flowchart illustrating
automatic control
processing of the work implement 13 in digging work.
[0036] As illustrated in FIG. 4, in step S101, the controller 26
acquires current
position data. At this time, the controller 26 acquires the current blade tip
position PO of
the blade 18 as described above.
[0037] In step S102, the controller 26 acquires design topography
data. As illustrated
in FIG. 5, the design topography data includes a height Zdesign of a final
design
topography 60 at a plurality of reference points Pn (n = 0, 1, 2, 3, ..., A)
in the traveling
direction of the work vehicle 1. The plurality of reference points Pn indicate
a plurality
of points at a predetermined interval along the traveling direction of the
work vehicle 1.
The plurality of reference points Pn are on the travel path of the blade 18.
In FIG. 5, the
final design topography 60 has a flat shape parallel to the horizontal
direction, but may
. . . .
CA 03061462 2019-10-24
have a different shape.
[0038] In step S103, the controller 26 acquires actual
topography data. The
controller 26 acquires the actual topography data by calculation from the work
site
topography data acquired from the storage device 28, and the vehicle body
position data
and traveling direction data acquired from the position sensor 31. The actual
topography
data is information indicating a topography positioned in the traveling
direction of the
work vehicle 1.
[0039] In step S104, the controller 26 performs smoothing
processing on the actual
topography data. FIG. 5 illustrates a cross section of an actual topography
50. In FIG. 5,
the vertical axis indicates the height of the topography, and the horizontal
axis indicates the
distance from the current position in the traveling direction of the work
vehicle 1.
[0040] Specifically, the actual topography data includes the
height Zn of the actual
topography 50 at the plurality of reference points Pn from the current
position to a
predetermined topography recognition distance dA in the traveling direction of
the work
vehicle 1. In the present embodiment, the current position is the position
determined
based on the current blade tip position PO of the work vehicle 1. The current
position
may be determined based on a current position of another portion of the work
vehicle 1.
The plurality of reference points are arranged at a predetermined interval,
for example,
every one meter.
[0041] In FIG. 5, an actual topography 50' illustrated by a
dashed line indicates the
actual topography data before the smoothing processing. The actual topography
50
illustrated by a solid line indicates the actual topography data after the
smoothing
processing. The term "smoothing" means processing to smooth variations in the
height of
the actual topography 50. For example, the controller 26 smooths the height Zn
at a
plurality of points of the actual topography 50 by the following formula (1).
z = (.En+2 z
n¨sm k=n-2 k)15 (1)
Zn_sm indicates the height of each point on the smoothed actual topography 50.
In the
following description, the simple term "actual topography 50" means the actual
topography
CA 03061462 2019-10-24
11
50 on which the smoothing processing is performed in step S104.
[0042] In step
S105, the controller 26 acquires a digging start position. For example,
the controller 26 acquires, as the digging start position, the position at
which the blade tip
position PO drops below the height ZO of the actual topography 50 for the
first time. As a
result, the position at which the tip of the blade 18 is lowered and digging
of the actual
topography 50 is started is acquired as the digging start position. However,
the controller
26 may acquire the digging start position by another method. For example, the
controller
26 may acquire the digging start position based on the operation of the second
operating
device 25b. Alternatively, the controller 26 may acquire the digging start
position by
calculating the optimal digging start position from the actual topography
data.
[0043] In step
S106, the controller 26 acquires a moving distance of the work vehicle 1.
The controller 26 acquires, as the moving distance, the distance traveled from
the digging
start position to the current position in the travel path of the blade 18. The
moving
distance of the work vehicle 1 may be a moving distance of the vehicle body
11.
Alternatively, the moving distance of the work vehicle 1 may be a moving
distance of the
tip of the blade 18.
[0044] In step
S107, the controller 26 determines target design topography data. The
target design topography data indicates a target design topography 70
illustrated by a
dashed line in FIG 6. The target design topography 70 indicates a desired
trajectory of
the tip of the blade 18 in work. In other words, the target design topography
70 indicates
a desired shape as a result of the digging work.
[0045] As
illustrated in FIG. 6, the controller 26 determines the target design
topography 70 displaced by a target displacement Z_offset downward from the
actual
topography 50. The target displacement Z_offset is the target displacement in
the vertical
direction at each reference point Pn. In the present embodiment, the target
displacement
Z_offset is a target depth at each reference point Pn, and indicates a target
position of the
blade 18 below the actual topography 50. The target position of the blade 18
means the
position of the tip of the blade 18. In other words, the target displacement
Z_offset
, = , CA 03061462 2019-10-24
12
indicates a soil amount per unit moving distance to be dug by the blade 18.
Therefore, the
target design topography data indicates the relation between the plurality of
reference
points Pn and a plurality of target soil amounts. The target displacement
Z_offset is an
example of a target parameter related to a target digging amount of the blade
18.
[0046] The controller 26 determines the target design topography
70 so that the target
design topography 70 does not go below the final design topography 60.
Therefore, the
controller 26 determines the target design topography 70 positioned at or
above the final
design topography 60 and below the actual topography 50 during the digging
work.
[0047] Specifically, the controller 26 determines the height Z of
the target design
topography 70 by the following formula (2).
Z = Zn-ti x Z_offset (2)
The target displacement Z_offset is determined by referring to a target
parameter data C.
The target parameter data C is stored in the storage device 28. ti is a
correction
coefficient according to an inclination degree parameter as described later.
Therefore,
when the correction by the correction coefficient ti is performed, a value
acquired by
multiplying Z_offset by ti is the corrected target displacement.
[0048] FIG. 7 is a graph illustrating an example of the target
parameter data C. The
target parameter data C defines the relation between a moving distance n of
the work
vehicle 1 and the target parameter. In the present embodiment, the target
parameter data
C defines the relation between the moving distance n of the work vehicle 1 and
the target
displacement Z_offset.
[0049] Specifically, the target parameter data C indicates a
digging depth (target
displacement) Z_offset of the blade 18 in the vertically downward direction
from the
ground surface as a dependent variable of the moving distance n of the work
vehicle 1 in
the horizontal direction. The moving distance n of the work vehicle 1 in the
horizontal
direction is substantially the same as the moving distance of the blade 18 in
the horizontal
direction. The controller 26 determines the target displacement Z_offset from
the moving
distance n of the work vehicle 1 by referring to the target parameter data C
illustrated in
. . CA 03061462 2019-10-24
13
FIG. 7.
[0050] As illustrated in FIG. 7, the target parameter data C
includes data at start cl,
data during digging c2, data during transition c3, and data during soil
transportation c4.
The data at start c 1 defines the relation between the moving distance n and
the target
displacement Z_offset in a digging start region. The digging start region is
the region
from a digging start point S to a steady digging start point D. As indicated
by the data at
start c 1, the target displacement Z_offset that increases as the moving
distance n increases
is defined in the digging start region.
[0051] The data during digging c2 defines the relation between
the moving distance n
and the target displacement Z_offset in a digging region. The digging region
is the region
from the steady digging start point D to a transitional soil transportation
start point T. As
indicated by the data during digging c2, the target displacement Z_offset is
defined to a
constant value in the digging region. The data during digging c2 defines a
constant target
displacement Z_offset with respect to the moving distance n.
[0052] The data during transition c3 defines the relation between
the moving distance
n and the target displacement Z_offset in a transitional soil transportation
region. The
transitional soil transportation region is the region from a steady digging
end point T to a
soil transportation start point P. The data during transition c3 defines the
target
displacement Z_offset that decreases as the moving distance n increases.
[0053] The data during soil transportation c4 defines the
relation between the moving
distance n and the target displacement Z_offset in a soil transportation
region. The soil
transportation region is the region starting from the soil transportation
start point P. As
indicated by the data during soil transportation c4, the target displacement
Z_offset is
defined to a constant value in the soil transportation region. The data during
soil
transportation c4 defines a constant target displacement Z_offset with respect
to the
moving distance n.
[0054] Specifically, the digging region starts at a first start
value b 1 and ends at a first
end value b2. The soil transportation region starts at a second start value
b3. The first
. = CA 03061462 2019-10-24
14
end value b2 is smaller than the second start value b3. Therefore, the digging
region
starts when the moving distance n in the digging region is less than the
moving distance n
in the soil transportation region. The target displacement Z_offset in the
digging region is
constant at a first target value al. The target displacement Z_offset in the
soil
transportation region is constant at a second target value a2. The first
target value al is
larger than the second target value a2. Therefore, the target displacement
Z_offset
defined in the digging region is larger than the target displacement Z_offset
in the soil
transportation region.
[0055]
The target displacement Z_offset at the digging start position is a start
value a0.
The start value a0 is smaller than the first target value al. The start target
value a0 is
smaller than the second target value a2.
[0056]
FIG. 8 is a flowchart illustrating processing for determining the target
displacement Z_offset. In order to simplify the following description, it is
assumed that
the work vehicle 1 travels only forward in the determination processing as
described below.
The determination processing starts when the first operating device 25a moves
to the
forward position. In step S201, the controller 26 determines whether the
moving distance
n is equal to or greater than zero and less than the first start value b 1 .
When the moving
distance n is equal to or greater than zero and less than the first start
value b 1, the
controller 26 gradually increases the target displacement Z_offset from the
start value a0 as
the moving distance n increases in step S202.
[0057]
The start value a0 is a constant and is stored in the storage device 28. The
start value a0 is preferably a small value at which the load on the blade 18
at the digging
start will not be excessively large. The first start value bl is acquired by
calculation from
an inclination c 1 in the digging start region, the start value a0, and the
first target value al
illustrated in FIG. 7. The inclination cl is a constant and is stored in the
storage device
28. The inclination c 1 is preferably a value at which a quick transition from
the digging
start to the digging work can be performed and the load on the blade 18 will
not be
excessively large.
. . . .
CA 03061462 2019-10-24
[0058] In step S203, the controller 26 determines whether the
moving distance n is
equal to or greater than the first start value b 1 and less than the first end
value b2. When
the moving distance n is equal to or greater than the first start value b 1
and less than the
first end value b2, the controller 26 sets the target displacement Z_offset to
the first target
value al in step S204. The first target value al is a constant and is stored
in the storage
device 28. The first target value al is preferably a value at which the
digging can be
performed efficiently and the load on the blade 18 will not be excessively
large.
[0059] In step S205, the controller 26 determines whether the
moving distance n is
equal to or greater than the first end value b2 and less than the second start
value b3.
When the moving distance n is equal to or greater than the first end value b2
and less than
the second start value b3, the controller 26 gradually decreases the target
displacement
Z_offset from the first target value al as the moving distance n increases in
step S206.
[0060] The first end value b2 is a moving distance at a time when
the current amount
of soil held by the blade 18 exceeds a predetermined threshold. Therefore,
when the
current amount of soil held by the blade 18 exceeds the predetermined
threshold, the
controller 26 decreases the target displacement Z_offset from the first target
value al.
The predetermined threshold is determined based, for example, on the maximum
capacity
of the blade 18. For example, the current amount of soil held by the blade 18
may be
determined by measuring a load on the blade 18 and by calculating from the
load.
Alternatively, the current amount of soil held by the blade 18 may be
calculated by
acquiring an image of the blade 18 with a camera and by analyzing the image.
[0061] At the start of work, a predetermined initial value is set
as the first end value b2.
After the start of work, the moving distance when the amount of soil held by
the blade 18
exceeds the predetermined threshold is stored as an updated value, and the
first end value
b2 is updated based on the stored updated value.
[0062] In step S207, the controller 26 determines whether the
moving distance n is
equal to or greater than the second start value b3. When the moving distance n
is equal to
or greater than the second start value b3, the controller 26 sets the target
displacement
. . CA 03061462 2019-10-24
16
Z_offset to the second target value a2 in step S208.
[0063] The second target value a2 is a constant and is stored in the
storage device 28.
The second target value a2 is preferably set to a value suitable for the soil
transportation
work. The second start value b3 is found by calculation from the inclination
c2 in the
transitional soil transportation region, the first target value al, and the
second target value
a2 illustrated in FIG. 7. The inclination c2 is a constant and is stored in
the storage
device 28. The inclination c2 is preferably a value at which a quick
transition from the
digging work to the soil transportation work can be performed and the load on
the blade 18
will not be excessively large.
[0064] The start value a0, the first target value al, and the second target
value a2 may
be changed according to a condition of the work vehicle 1 or the like. The
first start value
bl, the first end value b2, and the second start value b3 may be stored in the
storage device
28 as constants.
[0065] Next, processing for determining a correction coefficient ti
according to an
inclination degree parameter will be described. FIG. 9 is a flowchart
illustrating the
processing for determining the correction coefficient ti. As illustrated in
FIG. 9, the
controller 26 acquires an inclination degree parameter Svol in step S301. The
inclination
degree parameter Svol is the parameter indicating a degree of the inclination
of the actual
topography 50. A larger absolute value of the inclination degree parameter
Svol indicates
a greater degree of the inclination of the actual topography 50.
[0066] The controller 26 calculates a difference between a predetermined
horizontal
surface 80 and the actual topography 50 to determine the difference as the
inclination
degree parameter Svol. As illustrated in FIG. 10, the predetermined horizontal
surface 80
is the horizontal surface passing through the height of the actual topography
50 at the
digging start position. Alternatively, the horizontal surface 80 may be a
horizontal
surface passing through another position. For example, the horizontal surface
80 may be
a horizontal surface passing through the height of the actual topography 50 at
the current
position of the work vehicle 1.
i . CA 03061462 2019-10-24
17
[0067] The controller 26 determines, as the inclination degree parameter
Svol, the
difference between the horizontal surface 80 and the height Zn at each
reference point Pn
of the actual topography 50. Specifically, the controller 26 calculates the
inclination
degree parameter Svol by the following formula (3).
A
SV 01 = (EZn) I A¨ Zo (3)
That is, the inclination degree parameter Svol is the difference between the
height ZO of
the horizontal surface 80 and an average of the heights Zn of the actual
topography 50 at
the plurality of reference points Pn (n = 0, 1, ..., A) from the current
position to the
predetermined topography recognition distance dA. A positive value of the
inclination
degree parameter Svol indicates that the proportion of the upward gradient in
the actual
topography 50 is high. In addition, when the inclination degree parameter Svol
is a
positive value, a larger inclination degree parameter Svol indicates a steeper
inclination of
the upward gradient.
[0068] The inclination degree parameter Svol by the formula (3) may be
regarded as a
cross-sectional area between the actual topography 50 and the horizontal
surface 80 as
illustrated in FIG 11. In this case, the sum of the cross-sectional areas may
be determined
as the inclination degree parameter Svol, with the cross-sectional area
between the
horizontal surface 80 and the actual topography 50 positioned above the
horizontal surface
80 as a positive value, and with the cross-sectional area between the
horizontal surface 80
and the actual topography 50 positioned below the horizontal surface 80 as a
negative
value.
[0069] A negative value of the inclination degree parameter Svol indicates
that the
proportion of the downward gradient in the actual topography 50 is high. In
addition,
when the inclination degree parameter Svol is a negative value, a smaller
inclination
degree parameter Svol indicates a steeper inclination of the downward
gradient.
[0070] In step S302, the controller 26 determines whether the inclination
degree
parameter Svol is larger than a predetermined first threshold Si. The first
threshold Si is
. = . = CA 03061462 2019-10-24
18
a value for determining that the proportion of the upward gradient in the
actual topography
50 is high. Therefore, the controller 26 determines whether the actual
topography 50 is
an upward gradient according to the inclination degree parameter Svol. When
the
inclination degree parameter Svol is larger than the first threshold Si, the
process proceeds
to step S303.
[0071]
In step S303, the controller 26 determines the correction coefficient ti
according to the inclination degree parameter Svol. For example, the storage
device 28
may store data defining the relation between the inclination degree parameter
Svol and the
correction coefficient ti. The controller 26 may determine the correction
coefficient ti
according to the inclination degree parameter Svol by referring to the data.
[0072]
The correction coefficient tl is a positive value less than one. Therefore,
when the controller determines that the actual topography 50 is an upward
gradient, the
controller decreases a displacement amount of the target design topography 70
from the
actual topography 50 by multiplying the target displacement Z_offset by the
correction
coefficient ti.
When the inclination degree parameter Svol is larger than the
predetermined first threshold Si, a larger value of the inclination degree
parameter Svol
indicates a smaller correction coefficient ti.
[0073]
In step S302, when the inclination degree parameter Svol is equal to or less
than the first threshold Si, the process proceeds to step S304. In step S304,
the controller
26 determines whether the inclination degree parameter Svol is smaller than a
predetermined second threshold S2. The second threshold S2 is smaller than the
first
threshold Si. The second threshold S2 is a value for determining that the
proportion of
the downward gradient in the actual topography 50 is high. Therefore, the
controller 26
determines whether the actual topography 50 is a downward gradient according
to the
inclination degree parameter Svol. When the inclination degree parameter Svol
is smaller
than the second threshold S2, the process proceeds to step S305.
[0074]
In step S305, the controller 26 determines the correction coefficient tl
according to the inclination degree parameter Svol. When the inclination
degree
. = a .
CA 03061462 2019-10-24
19
parameter Svol is smaller than the second threshold S2, the correction
coefficient ti is a
value greater than one. Therefore, when the controller determines that the
actual
topography 50 is a downward gradient, the controller increases a displacement
amount of
the target design topography 70 from the actual topography 50 by multiplying
the target
displacement Z_offset by the correction coefficient ti. When the inclination
degree
parameter Svol is smaller than the predetermined second threshold S2, a
smaller value of
the inclination degree parameter Svol indicates a larger correction
coefficient ti.
[0075] In step S304, when the inclination degree parameter Svol
is equal to or greater
than the second threshold S2, the process proceeds to step S306. In step S306,
the
controller 26 sets the correction coefficient ti to one. That is, when the
inclination degree
parameter Svol is equal to or less than the first threshold Si and equal to or
greater than the
second threshold S2, the correction of the target displacement Z_offset by the
correction
coefficient ti is not performed.
[0076] As described above, the height Z of the target design
topography 70 is
determined from the aforementioned formula (2) by determining the target
displacement
Z_offset and the correction coefficient ti.
[0077] In step S108 illustrated in FIG. 4, the controller 26
controls the blade 18 toward
the target design topography 70. At this time, the controller 26 generates a
command
signal to the work implement 13 so that the tip position of the blade 18 moves
toward the
target design topography 70 generated in step S107. The generated command
signal is
input to the control valve 27. As a result, the blade tip position PO of the
work implement
13 moves along the target design topography 70.
[0078] In the aforementioned digging region, the target
displacement Z_offset between
the actual topography 50 and the target design topography 70 is large compared
to the
other regions. As a result, the digging work of the actual topography 50 is
performed in
the digging region. In the soil transportation region, the target displacement
Z_offset
between the actual topography 50 and the target design topography 70 is small
compared to
the other regions. As a result, the digging of the ground surface is
suppressed and the soil
CA 03061462 2019-10-24
held by the blade 18 is transported in the soil transportation region.
[0079] In step
S109, the controller 26 updates work site topography data. The
controller 26 updates the work site topography data according to position data
indicating
the latest trajectory of the blade tip position PO. Alternatively, the
controller 26 may
calculate the position of the bottom surface of the crawler belts 16 from the
vehicle body
position data and the vehicle body dimension data, and update the work site
topography
data according to the position data indicating the trajectory of the bottom
surface of the
crawler belts 16. In this case, the update of the work site topography data
can be
performed instantly.
[0080]
Alternatively, the work site topography data may be generated from survey data
measured by a survey device outside of the work vehicle 1. Aerial laser survey
may be
used as an external survey device, for example. Alternatively, the actual
topography 50
may be imaged by a camera, and the work site topography data may be generated
from the
image data captured by the camera. For example, aerial photographic survey
using an
unmanned aerial vehicle (UAV) may be used. In the case of using the external
survey
device or the camera, the work site topography data may be updated at a
predetermined
interval, or as needed.
[0081] The above
processing is executed when the work vehicle 1 moves forward.
For example, the above processing is executed when the first operating device
25a is in the
forward position. When the work vehicle 1 moves in reverse by a predetermined
distance
or more, the digging start position, the moving distance n, and the amount of
soil held by
the blade 18 are initialized.
[0082] The above
processing is executed when the work vehicle 1 moves forward
again. The controller 26 updates the actual topography 50 based on the updated
work site
topography data, and newly determines the target design topography 70 based on
the
updated actual topography 50. The controller 26 then controls the blade 18
along the
newly determined target design topography 70. This processing is repeated to
perform
digging so that the actual topography 50 approaches the final design
topography 60.
. . . . CA 03061462 2019-10-24
21
[0083]
In the above embodiment, the controller 26 repeats the processing from steps
S101 to S109 every time the work vehicle 1 moves forward by a predetermined
distance, or
at a predetermined time interval during moving forward. However, the
controller 26 may
repeat the processing from steps S101 to S109 every time the work vehicle 1
moves in
reverse by a predetermined distance, or at a predetermined time interval
during moving in
reverse.
[0084]
In the control system 3 of the work vehicle 1 according to the present
embodiment described above, the controller 26 determines whether the actual
topography
50 is an upward gradient or a downward gradient based on the actual topography
data, and
changes the target design topography 70 according to a result of
determination.
[0085]
Specifically, when the actual topography 50 is an upward gradient, the
correction coefficient ti is determined in such a manner that the displacement
amount of
the target design topography 70 from the actual topography 50 decreases. As a
result, the
target design topography 70 is changed. When the actual topography 50 is an
upward
gradient, the load on the work implement 13 tends to be large. Therefore, the
load on the
work implement 13 can be prevented from becoming excessive by changing the
target
design topography 70 as described above.
[0086]
When the actual topography 50 is a downward gradient, the correction
coefficient ti is determined in such a manner that the displacement amount of
the target
design topography 70 from the actual topography 50 increases. As a result, the
target
design topography 70 is changed. When the actual topography 50 is a downward
gradient,
the load on the work implement 13 tends to be small. Therefore, the amount of
soil to be
dug by the work implement 13 can be increased by changing the target design
topography
70 as described above. As a result, work efficiency can be improved.
[0087]
Further, when the inclination degree parameter Svol is larger than the first
threshold Si, a larger value of the inclination degree parameter Svol
indicates a smaller
correction coefficient ti. When the actual topography 50 is an upward
gradient, a larger
value of the inclination degree parameter Svol indicates a steeper inclination
of the upward
. . CA 03061462 2019-10-24
22
gradient. Therefore, as the inclination of the upward gradient is steeper, the
correction
coefficient ti decreases. As a result, the displacement amount of the target
design
topography 70 from the actual topography 50 decreases. This enables to
determine the
displacement amount of the target design topography 70 appropriately according
to the
degree of the inclination of the upward gradient.
[0088]
When the inclination degree parameter Svol is smaller than the second
threshold S2, a smaller value of the inclination degree parameter Svol
indicates a larger
correction coefficient ti. When the actual topography 50 is a downward
gradient, a
smaller value of the inclination degree parameter Svol indicates a steeper
inclination of the
downward gradient. Therefore, as the inclination of the downward gradient is
steeper, the
correction coefficient ti increases. As a result, the displacement amount of
the target
design topography 70 from the actual topography 50 increases. This enables to
determine
the displacement amount of the target design topography 70 appropriately
according to the
degree of the inclination of the downward gradient.
[0089]
Although an embodiment of the present invention has been described so far,
the
present invention is not limited to the above embodiment and various
modifications may be
made within the scope of the invention.
[0090]
The work vehicle 1 is not limited to the bulldozer, and may be another
vehicle
such as a wheel loader or a motor grader.
[0091]
The work vehicle 1 may be remotely operable. In this case, a portion of the
control system 3 may be disposed outside of the work vehicle 1. For example,
the
controller 26 may be disposed outside of the work vehicle 1. The controller 26
may be
disposed inside a control center separated from the work site.
[0092]
The controller 26 may have a plurality of controllers 26 separated from one
another. For example, as illustrated in FIG. 12, the controller 26 may include
a remote
controller 261 disposed outside of the work vehicle 1 and an onboard
controller 262
mounted on the work vehicle 1. The remote controller 261 and the onboard
controller
262 may be able to communicate wirelessly via the communication devices 38 and
39.
. . CA 03061462 2019-10-24
23
Some of the aforementioned functions of the controller 26 may be executed by
the remote
controller 261, and the remaining functions may be executed by the onboard
controller 262.
For example, the processing for determining the target design topography 70
may be
executed by the remote controller 261, and the processing for outputting a
command signal
to the work implement 13 may be executed by the onboard controller 262.
[0093] The operating devices 25a and 25b, the input device 25c,
and the display 25d
may be disposed outside the work vehicle 1. In this case, the operating cabin
may be
omitted from the work vehicle 1. Alternatively, the operating devices 25a and
25b, the
input device 25c, and the display 25d may be omitted from the work vehicle 1.
The work
vehicle 1 may be operated only by the automatic control by the controller 26
without
operation of the operating devices 25a and 25b.
[0094] The actual topography 50 may be acquired by another
device, instead of the
aforementioned position sensor 31. For example, as illustrated in FIG. 13, the
actual
topography 50 may be acquired by an interface device 37 that receives data
from an
external device. The interface device 37 may wirelessly receive the actual
topography
data measured by an external measuring device 41. Alternatively, the interface
device 37
may be a recording medium reading device and may receive the actual topography
data
measured by the external measuring device 41 via the recording medium.
[0095] The target parameter data is not limited to the data
illustrated in FIG. 7 and
may be changed. The target parameter is the parameter related to the target
digging
amount of the work implement 13 and is not limited to the target displacement
of the above
embodiment, and may be another parameter. For example, FIG. 14 is a graph
illustrating
another example of the target parameter data.
[0096] As illustrated in FIG. 14, the target parameter may be a
target soil amount
S_target at each point in a flat topography. That is, the target parameter may
be the target
soil amount S_target per unit distance. For example, the controller 26 can
calculate the
target displacement Z_offset from the target soil amount S_target and the
width of the
blade 18. Alternatively, the target parameter may be a parameter different
from the target
. .. . .
CA 03061462 2019-10-24
24
soil amount S_target per unit distance. For example, the target parameter may
be a
parameter indicating a target value of the load on the work implement 13 at
each point.
The controller 26 can calculate the target displacement Z_offset at each point
from the
target parameter.
In this case, the controller 26 may increase the target displacement
Z_offset as the target parameter increases.
[0097]
The target displacement Z_offset may be multiplied by a predetermined
coefficient other than ti. Alternatively, a predetermined constant may be
added to or
subtracted from the target displacement Z_offset. The predetermined
coefficient and the
predetermined constant may be changed according to the change of the control
mode.
[0098]
In the smoothing processing indicated by the above formula (1), the average
of
the height of five points is calculated. However, the number of points used
for smoothing
may be less than five or greater than five. The number of points used for
smoothing can
be varied, and the operator can set the desired degree of smoothing by
changing the
number of points used for smoothing.
[0099]
Also, the average to be calculated is not limited to the average of the
height of
the points to be smoothed and points ahead and behind, but also the average of
the height
of the points to be smoothed and points located in front. Alternatively, the
average of the
height of the points to be smoothed and points located behind may be
calculated.
Alternatively, the smoothing processing is not limited to the method using
average but also
another smoothing processing such as least squares method or n-order
approximation may
be used. Alternatively, the smoothing processing may be omitted.
[0100]
In the above embodiment, the inclination degree parameter Svol is the
difference between the average of the height of the actual topography 50 and
the height of
the horizontal surface 80 but is not limited to the aforementioned embodiment
as long as
the inclination degree parameter Svol indicates the direction and degree of
the inclination
of the gradient. For example, the inclination degree parameter Svol may be a
volume
instead of the cross-sectional area between the actual topography 50 and the
horizontal
surface 80.
. . CA 03061462 2019-10-24
[0101]
Alternatively, the controller 26 may calculate an inclination angle of the
actual
topography 50 and determine the inclination angle as the inclination degree
parameter Svol.
For example, as illustrated in FIG. 15, the controller calculates an
inclination An (n = 0,
1,... , A) of a straight line Ln connecting any two reference points of the
actual topography
50.
The inclination An of the straight line Ln connecting any two reference
points of the
actual topography 50 is calculated by the following formula (4).
An = (Zn+Nref ¨ Zil Nref (4)
Nref is a value indicating the interval between two reference points. For
example, when
Nref is four, the inclination An is the inclination of the straight line
connecting any one
reference point and the fourth reference point counting from the reference
point in the
traveling direction of the work vehicle 1. The controller 26 acquires the
aforementioned
inclination An (n = 0, 1,... , A) with respect to the plurality of reference
points Pn from the
current position to the predetermined topography recognition distance dA. The
controller
26 may determine the minimum value, the maximum value, or the average of the
inclination An (n = 0, 1,... , A) as the inclination degree parameter Svol.
[0102]
The controller 26 may acquire the actual topography data within a shorter
range
than the predetermined topography recognition distance dA from the current
position.
That is, the controller 26 may acquire the actual topography data with respect
to only a
portion of the plurality of reference points Pn. The controller 26 may
determine the target
design topography 70 within a shorter range than the predetermined topography
recognition distance dA from the current position. That is, the controller 26
may
determine the target design topography 70 with reference to only a portion of
the plurality
of reference points Pn.
INDUSTRIAL APPLICABILITY
[0103]
In the present invention, the target design topography is determined based on
the actual topography, and the target design topography is changed according
to a result of
determination as to whether the actual topography is an upward gradient or a
downward
CA 03061462 2019-10-24
26
gradient. As a result, the load on the work implement can be prevented from
becoming
excessive while work efficiency can be improved.
REFERENCE SIGNS LIST
[0104] 13 Work implement
1 Work vehicle
28 Storage device
26 Controller
31 Position sensor
